sustainability Article Techno-Economic Assessment of Battery Electric Trains and Recharging Infrastructure Alternatives Integrating Adjacent Renewable Energy Sources Christoph Streuling 1,* , Johannes Pagenkopf 1, Moritz Schenker 1 and Kim Lakeit 2 1 German Aerospace Center (DLR), Institute of Vehicle Concepts, 70569 Stuttgart, Germany; [email protected] (J.P.); [email protected] (M.S.) 2 Institute of Electric Power Systems, Otto von Guericke University, 39106 Magdeburg, Germany; [email protected] * Correspondence: [email protected] Abstract: Battery electric multiple units (BEMU) are an effective path towards a decarbonized regional rail transport on partly electrified rail lines. As a means of sector coupling, the BEMU recharging energy demand provided through overhead line islands can be covered from decentralized renewable energy sources (RES). Thus, fully carbon-free electricity for rail transport purposes can be obtained. In this study, we analyze cost reduction potentials of efficient recharging infrastructure positioning and the feasibility of covering BEMU energy demand by direct-use of locally produced renewable electricity. Therefore, we set up a model-based approach which assesses relevant lifecycle costs (LCC) of different trackside electrification alternatives comparing energy supply from local RES and grid consumption. The model-based approach is applied to the example of a German regional rail line. In Citation: Streuling, C.; Pagenkopf, J.; the case of an overhead line island, the direct-use of electricity from adjacent wind power plants with Schenker, M.; Lakeit, K. on-site battery storage results in relevant LCC of EUR 173.4 M/30a, while grid consumption results in Techno-Economic Assessment of EUR 176.2 M/30a whereas full electrification results in EUR 224.5 M/30a. Depending on site-specific Battery Electric Trains and factors such as existing electrification and line lengths, BEMU operation and partial overhead line Recharging Infrastructure extension can lead to significant cost reductions of recharging infrastructure as compared to full Alternatives Integrating Adjacent Renewable Energy Sources. electrification. Sustainability 2021, 13, 8234. https:// doi.org/10.3390/su13158234 Keywords: battery electric train; multiple unit; regional rail passenger service; direct-use of local renewable energy sources; on-site battery storage; sector coupling; lifecycle cost Academic Editor: Aritra Ghosh Received: 31 May 2021 Accepted: 14 July 2021 1. Introduction Published: 23 July 2021 1.1. Background Aiming for the decarbonization of the transport sector, the substitution of diesel- Publisher’s Note: MDPI stays neutral powered vehicles by zero-tailpipe alternatives is broadly discussed. Within the public with regard to jurisdictional claims in transport sector, the deployment of battery-powered electric bus and train systems plays published maps and institutional affil- an important role to increase energy efficiency and to abate emissions. iations. About 54% of the German rail network is not electrified [1]. In 2017, regional rail transport in Germany accounted for 680.5 million train-km, of which about 36% had been operated with trains in diesel traction (diesel multiple units—DMU). In current public tenders for transport contracts in German regional rail transport, more than 305.1 million Copyright: © 2021 by the authors. train-km are to be allocated to tenderers for both battery electric multiple units (BEMU) Licensee MDPI, Basel, Switzerland. and fuel-cell electric multiple units (FCEMU), till 2038 [1] (p. 158). Aiming for locally This article is an open access article emission-free operation, the future regional rail traffic capacity yields a cumulated demand distributed under the terms and of 1768 to 2560 trains with zero-tail-pipe drivetrains till 2038 in Germany [1] (p. 164). conditions of the Creative Commons According to the German Federal Ministry of Transport and Digital Infrastructure Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ (BMVI) [2], the electrification of the German rail network will be increased to 70% in 4.0/). a mid-term time horizon. Due to high capital expenditures (CAPEX) of overhead line Sustainability 2021, 13, 8234. https://doi.org/10.3390/su13158234 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, 8234 2 of 30 (OHL) equipment, economic feasibility of full electrification is usually only yielded at train service frequencies of one or more trainsets per hour (for 2-car multiple units) [3]. On those non- or partly electrified tracks, the substitution of trains equipped with internal combustion engines by multiple units with locally emission-free drivetrains, such as BEMU and FCEMU, offer a cost-effective alternative against full lineside electrification [1,4]. Both drivetrain-technologies are interlinked to an appropriate energy infrastructure providing the charging electricity from OHL or hydrogen from refueling stations. The technical feasibility and assessment of lifecycle costs (LCC) of regional train transport with zero-tailpipe drivetrain multiple units is subject to several feasibility studies, especially in German research [4–7]. The results show a strong dependency on the rail line and network characteristics, such as grid topology, length of line, electrified sections and schedule. The replacement with BEMU on railway-lines with non-electrified section-lengths of less than 40 km (one-way) and an electrified start- or end-station may not necessarily require further recharging infrastructure in every case. Railway manufacturers claim catenary-free autonomies of BEMU trains in the range of 60 to 100 km [1,4] while this parameter also varies depending on the rail-line and schedule characteristics. 1.2. Positioning of Recharging Infrastructure and Sector Coupling with Adjacent RES The balancing of electrification extensions against the size of battery is subject to model-based analysis, as being discussed by Royston et al., 2019 [8] at the example regional rail route in the United Kingdom. Battery storage capacities of the BEMU and charging infrastructure have to be designed according to well-defined operational worst-case con- ditions (e.g., winter, delays, track interruptions, end-of-life conditions) in order to also secure transport-operation at difficult—while not exceptional—operational conditions. The vehicle energy demand of traction, HVAC (heating, ventilation and air conditioning), sec- ondary auxiliaries and the additional energy demand caused by external disturbances and incidents have to be covered by an appropriate battery management system [7]. The energy demand characteristic of BEMU at charging substations results in predictable punctual high loads on the electricity grids, especially when substations are connected to the public electricity grid at medium voltage. The energy demand of BEMU, recharged at newly constructed charging stations or short electrified island sections, can be covered by local RES especially in rural areas. The coupling of BEMU recharging facilities and local RES requires the use of a stationary storage to synchronize the fluctuating energy supply characteristics and the punctual energy demand of BEMU. Integrating RES for direct electricity use, the storage system has to meet the requirements of both high power and high capacity. Hence, chemical power-to-gas storage systems are less likely to be considered [9]. In the field of scheduled public transport, regional trains and buses show similar oper- ation conditions in terms of fixed routes and dwell times, resulting in predictable energy demands at charging spots. The combination of recharging infrastructure and batteries of railway multiple units need a reliable energy supply to maintain a stable operation even under demanding conditions, as discussed in studies concerning bus-networks [10–12]. An efficient layout of the charging infrastructure and an appropriate dimensioning of battery capacity is crucial to minimize the total cost of ownership according to Kunith (2016) [10]. Kunith (2016) [10] and Rogge (2015) [11] present approaches for positioning of charging stations in bus networks using model-based analyses. Vilppo (2015) [12] conducted di- mensioning of the traction battery according to peak-load requirements. Rogge (2015) [11] discussed the impact on the electricity grid based on the load profiles of a selected charging station and a combined load profile of the entire network. 1.3. Research Objectives and Approach Little attention in academic literature has been put to model-based analysis investigat- ing layout and positioning of recharging infrastructure for BEMU. The impact of charging Sustainability 2021, 13, 8234 3 of 30 infrastructure positioning and specification on the relevant LCC has not been discussed in detail. While hydrogen costs for FCEMU refueling with hydrogen from onsite electrolysis based on electricity produced from local wind power plants (WPP) have been analyzed in Herwartz (2020) [5], the feasibility and cost assessment of BEMU recharging with electricity produced from local RES has not yet been investigated. This study aims to evaluate the cost reduction potentials of efficient positioning of BEMU recharging infrastructure on non or partly electrified railway lines of the German regional rail passenger transport which are currently operated by DMU. Further, we assess the sector coupling potential of BEMU recharging infrastructure and adjacent RES. First, we classify way-side electrification alternatives and discuss